Variable capacity pump



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VARIABLE CAPACITY PUMP FiledvJuly 21, 194.3 6 Sheets-$hect 3 INVENTOR DESIRE J. DESCHAMPS BY m 9 film/1M .y ATTORNEY-S 1947. D. J. DESCHAMPS VARIABLE CAPACITY PUMP 6 Sheets-Sheet 4 Filed July 21, 1943 kowkm ks A vQ Em 93 53% a e? 3% .2 nwashofiawb w QPSJQQ ,9 3 2 03 .2 v U2 0% 5 M I P 5 R Y o M E MM w .10 m w n D A J W E Y I R B m 5 E 01 0 1947. D. J. DESCHAMPS 2,431,

VARIABLE CAPACITY PUMP -Filed July 21, 1943 6 Sheets-Sheet 5 INVENTOR DESIRE J. DEscHAMPs I ATTORNEYS Dec. 2, 1947. D. J. DESCHAMPS VARIABLE CAPACITY PUMP Filed July 21, 1943 6 Sheets-Sheet 6 INVENTOR Dssmz J'. DEscHAMPs film,

WM :1 aawa ATTORNEYS Patented Dec. 2, 1947 UNITED STATES PATENT OFFICE VARIABLE CAPACITY PUMP Desire J. lleschamps, Rutherford, N. 1.,asslgnor to Deschamps Fuel Injection Corporation, New York, N. Y. a corporation of New York Application July 21, 1943, Serial No. 495,541

. 23 Claims. 4 1

This invention relates to variable capacity hydraulic pumps of the positive displacement type, and, more particularly, to' pumps provided with one ormore cylinders and cooperating pistons or plungers and which are capable of operation at either low or high pressures, the general object of the invention being to provide an improved variable capacity pump. I

The invention aims to provide a piston-andcylinder type of pump in which the capacity or output of the pump can be continuously varied and controlled with great accuracy while the pump is in operation.

Another feature of the invention is the provision of a construction by which an accurate metering of the pump output is obtained not only when pumping near the rated capacity of the pump but also when the pump is delivering small quantities of liquid.

Another object of the invention is to provide a pump construction in which the output varies in equal amounts for equal changes in the setting of the pump capacity control member.

An object of the invention also is to provide a positive displacement pump in which very little force is required to actuate the control member to vary the output from zero to maximum.

Another object of the invention is to provide a pump with substantially a "straight-line delivery, meaning that for a given setting of the capacity control member, the output increases and decreases substantially in a straight ratio with speed.

Pumps of the type contemplated by the invention have a variety of applications, one of their important uses being to supply fuel to the air intake pipe of an internal combustion engine in conjunction with appropriate control mechanism to proportion the fuel and air in accordance with the demands of the engine, as is done, for example, in supplying fuel mixtures to certain types of aircraft enginesthe so-called non-timed injection. The invention will be described as embodied in a pump intended for such use.

Diiilculty has been experienced in the operation of such engines with non-timed injection because the pulsating character of the flow from the fuel pump was reflected in the performance of the engine when operating at low speeds, causing the engine to surge.

An additional object of the invention is, therefore, to overcome such difliculty and to provide a variable output positive displacement hydraulic pump which delivers a substantially non-pulsating flow regardless of the pumps output adjustmentfrom the maximum output down to substantially zero output.

In connection with pumps for handling fuel such as gasoline it is important to prevent the leakage of the fuel into the lubricating system of the pump and engine. In view of the fact also that such pumps are required to operate at such substantial pressures as above mentioned and to deliver sizable quantities of fue1,in gallons per minute when the engine is operating at full power output, and even when the engine is operating at cruising power, difllculties are encountered in connection with adequate lubrication. It is also an object of the present invention to overcome such lubrication difliculties and to prevent the dilution of the lubricant by the fuel.

The invention will be understood from a consideration of the accompanying drawings exemplifying one of its embodiments. In these drawings:

Fig. l is a view of the pump in central longitudinal section taken on line l-l of Figs; 5 and Fig. 2 is a fragmentary section similar to Fig. 1 showing the plungers in diiferent position;

Fig. 3 is a detailed view of the pump shaft and its associated parts with certain parts shown in longitudinal section;

Fig. 4 is a transverse section taken on line 44 of Fig. 3;

Fig. 5 is a central transverse section taken on line 5-5 of Fig. 1 showing the inlet passages;

Fi 6 is a view of the pump in side elevation with parts broken away and showing a vertical section taken on line 6-6 of Fig. 5;

Fig. 7 is a transverse section taken on line l- -1 of Fig. 1 showing the outlet passages;

Fig. 8 is a sectional view taken on broken line 88 of Fig. '7 showing the outlet valve for one of the cylinders;

Fig. 9 is a transverse section taken on line 9-9 of Fig. 1 looking in the direction of the arrows;

Fig. 10 is a diagramshowing the travel of the two plungers of a cylinder with the wobble plate plunger driving cams set at three different angular (or phase) positions and also indicating'the effective strokes for these different settings;

Figs. 11 and 12 are diagrams showing the effective strokes for two additional angular settings of the wobble plate cams;

Fig. 13 is a diagram showing the variation of the length of the effective stroke (or output) of the pump with change of the angular setting of the wobble plate cams:

Fig. 14 is a fragmentary vertical section looking from the rear of the pump at the right hand end Fig. 16 is a view partly in section on the line l9-l9 of Fig. 15 showing the lubricating oil inlet passages; and

Fig. 17 is a view showing a modification of the mechanism for adjusting the angular setting of the wobble plate cams.

Referring now to the accompanying drawings, the pump housing or casing comprises a center section i, a front section 2 and a rear section 3. Center section I of the housing has a cylindrical bore 4 within which is mounted a cylindrical cylinder block 3. Block I is hollow at the center for the passage of the pump shaft and surrounding this central opening there is a plurality (in this instance 5) of pump cylinder members, or liners, or bushings. 9. These are each provided at their right hand ends with a flange I and are forced into suitable openings formed in cylinder block 5.

The front section 2 of the pump housing is secured to center section i by means of a series of tap bolts 9 and is provided with a flange 9 having appropriate bolt holes, as shown in Fig.

In order to admit liquid into the pumping space It, cylinder 9 is provided with four inlet ports 22 (see Figs. 1 and 5) which open into two drilled I passageways 23 in the cylinder block 5 which, in

turn, open into a circular inlet chamber 24. The

liquid to be pumped, such as gasoline, enters the pump through an inlet connection (Fig. 6) and enters the .open end of a cup-shaped filter element 29. After passing through-the walls of the filtering element it is received within a surrounding space 21 and flows through a connecting passage 23 into circular inlet chamber 24.

Filter element 29 is arranged to be removed for cleaning and replacement and for this purpose is attached at its closed end to a supporting cover member 29 (Fig. 6) which closes an opening 39 order to prevent the leakage of unfiltered liquid 15, by means of which the pump is mounted upon a suitable support, such as the mounting pad l9 (Fig. 16) which is provided on the frame I I of the aircraft engine.v supports the front ball bearing [2 of the pump.

Rear casing section 3 of the pump is mounted upon the center section I by means of a series of tap bolts l3 and supports the rear pump bearing I4. It also houses the pump capacity varying mechanism which is actuated by the capacitychanging or output lever I5.

The pump cylinders 9 are identical with one another and a description of one of these cylinders and its associated parts is applicable to all. Each cylinder 6, as shown in Fig. l, is provided with two pistons or plungers l6 and I1 whose inner ends cooperate to define between them a common working or pumping space ll. These plungers are actuated by means of two fixed stroke wobble plate cams I 9 and 2llwhich are mounted on the pump main shaft 2| in such a way as to be adjustably rotatable on this shaft to vary the phase angle of the cams while the pump is in operation. The change in the operation of plungers I9 and i1 thus produced varies the effective stroke of the pump.

This may be readily understood by observing that in Fig. 1 the wobble plate cams l9 and 29 are positioned in phase with each other or, in other words. at 0 with one another. Plungers l6 and I] therefore also move in phase with one another, plunger l9, for example, moving simultaneously with plunger ll in the same direction and to the same extent so that there is no change in the volume of space l8, the liquid contained therein being simply moved back and forth within cylinder 6. That is to say, the effective stroke is zero.

If, however, the wobble plates l9 and 29 are placed at some angle other than 0 with respect to each other, plungers l6 and I! will not move in phase with each other and the volume of pumping space l8 will shrink and expand with each rotation of shaft 2|; in other words, the pump will have an effective stroke'and its amount will depend upon the relative angular positions of wobble plates l9 and 29.

Front casing section 2 also through the filter.

Cover member 29 is held in position by one or more nuts 33 which clamp the member in opening 39 against a suitable washer 34, and simultaneously force the inner cylindrical end of filter element 29 against a washer 33 which is mounted on a flange member 39 placed inwardly of inlet connection 23.

' fluids, as in conjunction with an engine fuel system, it is necessary to remove air and vapor because their presence in pumping chambers l3 would cause irregular operation and inaccurate control of the pump output. The greater part is removed by a vapor eliminator, and two outlets 36' are provided, both of which are shown in the drawings with plugs in them. These two outlets enable the pump to be mounted in either of two positions on the mounting pad of the engine, and the plug which is at the top is to be removed and a connection made to the vapor eliminator.

Alongside of circular inlet chamber 24 is an outlet chamber 31. The main pump outlet connection 39 is shown in Fig. '7. Each of the cylinders 9 is provided with an outlet port 39 (see Figs. 8 and 2). This opens out of a circular groove 40 surrounding the inner end of plunger I! when it is at the inner end of its stroke in order to prevent plunger H from closing outlet port 39, for although plunger [9 controls the opening and closing of the inlet ports 22, plunger Il does not control outlet port 39.

In a variable output positive displacement hydraulic pump used for fuel injection it is important to prevent side thrust of the plunger against the walls of the cylinders or bushings, as this would ultimately interfere with the accurate metering ability of the pump. Circular groove 40 extends entirely around the mid-section of the cylinder and for a substantial distance lengthwise adjacent the end of plunger II, when it is near the inner end of its stroke, having substantially the same width as port 39. Thus it provides a free path for the flow of the liquid towards port 39 and also places the end of the plunger in hydraulic balance.

Outlet :port 39 communicates with an L-shaped passage ll in cylinder block 5 and, mounted in the outer leg of this passage, there is an automatic outlet valve (or check valve) 42. This is a cup-shaped member which seats upon a shoulder formed in the outer leg of L-shaped passage 4| and when lifted from this seat by the pressure of the liquid. permits the liquid to flow through a pair of drilled passages 43 (Fig. 7) in cylinder block 5 which register with an opening 44 in housing Thus the liquid enters the circular outlet chamber 31.

A helical spring 45 serves to bias valve 42 against its seat and is held in position by means of a removable plug 46 threaded into cylinder block 5. It will be understood that there is an outlet valve 42 and the connecting passages just described for each of the five cylinders 6.

It will be understood that the plungers l6 and H are moved inwardly by the respective wobble plate cams l9 and 28 and are moved outwardly by means of helical springs as shown at 41 in Figs. 1 and 16. For the purpose of transmitting the actuating force from cams l9 and 20 to the plungers, each of the plungers is provided at its outer end with a slipper or shoe 48 which is so mounted on the plunger as to maintain its bearing surface in contact with the flat face of its cooperating wobble plate cam regardless of the angular position the plunger may have with respect to the cam during a complete revolution.

In a pump of this type in which the output of each cylinder is very accurately controlled and wherein such accurate control of the output must be maintained throughout a long period of service, it is not only important but very necessary to prevent tilting of the bearing surface of the slipper with respect to the face of the wobble plate. If such tilting is permitted the bearing face of the slipper will be caused to wear unevenly, even to such an extent that the face of the slippers may become convex in shape. Such a condition would make accurate metering impossible.

To bring about absence of a tilting moment on slippers 48 they are arranged to have a center of oscillation on the plunger which is substantially in the plane of the wobble plate bearin face. Slippers 48 are made semispherical in shape and are so mounted that the center of the semispherical surface of the slipper lies in, or substantially in, the plane of the bearing surface of the slipper on the face of the wobble plate. The semispherical surface of slipper 46 is received in a similarly shaped socket 49 formed on the inside of a head member 50 which is preferably formed integrally with the body of plungers l6 and H at their outer ends. Head portion 50 has a rim 5| against which bears the operating spring 41.

In order to retain the slipper 48 in the socket thus formed, the slipper is made hollow at the center to receive the head 52 of a retainer 53 which is fitted within a bore in the outer end of the plunger and held therein by means of a cross pin 54. Retainer head 52 also has a semispherical under surface which is concentric with the socket surface 49 of head 50. surface 55 of slipper 48 is of semispherical shape to cooperate with the head 52 so that both the interior and exterior surfaces of slipper 48 are concentric. Head 52 is attached to retainer 53 by a narrow neck portion 56 which passes through a larger opening 51 in slipper 48 in order to permit the necessary freedom of movement to the slipper,

The mounting of the wobble plate cams I9 and 20 and the mechanism for adjusting their relative angular positions on shaft 2| while the pump The interior 6 is operating in order to vary the output .oncapacity will now be described.

Main shaft 2| of the pump is splinedat its outer end as indicated at 58 to provide a driving connection with the aircraft engine when the pump is mounted thereon. Shaft 2| extends into the pump to a point a short distance to the left of the right hand bearing l4 and about midway of its length is provided with two oppositely positioned bosses against which lie the inner faces of two bevel gears 59 which might be said to form the planet pinions of a differential gear mechanism. Gears 59 rotate on a hollow shaft 60 which passes through a cross bore in shaft 2| at the centers of the two bosses previously referred to. The gears are retained in place on hollow shaft 60 by means of washers 8| and a hollow rivet 62. Shaft 2| is preferably made hollow in the interest of lightness.

' The wobble plate cam 26 at the left hand end of the pump is integral with or fixed to a sleeve 63 which closely fits the exterior surface of shaft 2|, this sleeve being provided at its inner end with bevelled teeth 64 which engage the teeth of bevel gears 59. Sleeve 63 has at its outer end an enlarged hub portion 65 which serves to strengthen wobble plate 20 and also to support the inner race of ball bearing I 2.

Wobble plate cam l9 at the right hand end of the pump is fixed near the outer end of a second sleeve 66 which closely fits the surface of pump shaft 2| but is longer than sleeve 63 and extends for a considerable distance beyond the end of shaft 2|. Sleeve 66 at its outer or right hand end beyond cam |9 supports the inner race of the right hand pump bearing l4. At its inner end sleeve 66, like sleeve 63, is provided with teeth 61 which engage the teeth of bevel gears 59.

With such a construction the torque for driving or rotating the wobble plate cams l9 and 20 is transmitted from shaft 2| through the differential gear mechanism comprising bevel gears or planet pinions 59 and sun gears 64 and 61, but the wobble plates will tend to rotate to the position where they are in phase with one another, or, in other words, where the output of the pump is zero. At this position the wobble plates may be said to have an offset of 0.

With the arrangement just described, the rotation of one of the wobble plate cams |9 with respect to shaft 2| in a given direction will cause an equal and opposite rotation of the other wobble plate cam 20. Mechanism is provided for rotating the wobble plates in this manner with respect to one another so as to adjust their offset angle away from the 0 position to cause the pump to produce the desired output and to maintain the wobble plates in such position.

This mechanism includes an offset adjusting member 68 in the form of a hollow sleeve having internal helical splines 69 which engage similar splines 16 provided on the outside of main shaft and extending to the left from its right hand end to enable offset adjusting member or sleeve 68 to be moved axially on shaft 2| to cause it to rotate with respect to the shaft through a predetermined angle.

Such rotation of offset adjusting member 68 is transmitted to sleeve 66 by means of a key H fixed in a groove in member 68 of the same length as the key. Key 1| slides longitudinally in an elongated slot 12 cut in an enlarged portion 13 of sleeve 66, this enlargement being provided in order to accommodate ofiset adjusting mem-. ber 68. Key H is held in place by a thin walled sleeve 14 which is slipped over enlarged portion 13.

The offset adjusting member 68 is movable longitudinally by the output control lever l and the connections between them are shown in Fig. l. Lever I5 is fixed upon the outer end or a shaft which projects through the wall of the rear section 3 of the pump housing (see also Figs. 9 and 14). A yoke 16 is fixed to the inner end of shaft 15 and has a link 11 pivoted to it at its outer end at 18. The other end of link 11 is pivoted at 19 to a member 80 which is connected to ofiset adjusting member 68 by means of a pair of ball thrust bearings thereby enabling member 68 to be moved longitudinally by member 88 while member 68 is rotating with the pump shaft 2|.

From this description it will be understood that movement of output control lever I5 from the position shown in Fig. l, in a counterclockwise direction, will cause offset control member 68 to slide toward the left on shaft 2|, with the result that wobble plate cam l9 will be rotated with respect to shaft 2| and through the differential gearing wobble plate 20 will be rotated an equal amount inthe opposite direction. This movement will therefore place wobble plates [9 and 28 out of phase with each other and cause the pump to deliver liquid, the output being at a maximum when the left hand end of offset adjusting member 68 is in contact with the shoulder formed at the bottom of enlargement l3.

The arrangement of the parts can be made to utilize any desired angular movement of output control lever l5, but in order to suit a particular automatic control mechanism with which this embodiment of the improved pump is intended to be used, lever I5 is arranged to have a total angular movement of 65 which, if desired, may be indicated on an indicator dial 8| (Figs. 14 and 9). An indicator 82 aflixed to shaft 15 may be arranged to show the position of the output control mechanism on this dial.

It has become almost universal practice in manufacturing aircraft engines to make provision to use oil under pressure from the main engine lubricating system for lubricating engine-driven accessories, such for example, as this pump. The mounting pad Ill (Fig. 16) on the engine thus has an oil supply passage 83 which usually would be located in the position indicated in Fig. 15. Because of the construction of the pump, however, it is more convenient to locate the oil inlet to the pump at 84. To connect the engine supply passage 83 with oil inlet 84 a circular groove 85 is machined in the face of pump mounting flange 9; then a short slot 86 is milled in flange 9 to connect this groove with the oil inlet tube 84 and another short slot 81 to connect inlet 83 with groove 85. In order to allow the mounting of the pump in four different angular positions and have communication with the oil supply 83 at each, three additional short slots 81 are milled in flange 9.

From inlet tube 84 the oil flows through a drilled passage 88 in the central section I of the pump housing, to a circular groove 89 formed in the, .cylindrical surface of cylinder block 5. In case the mounting pad on the engine has not been drilled for an oil connection, the oil is supplied to passage 88 through an outside oil line which is connected to passage 88a. When the mounting pad is provided with an .oil supply port 83, then passage 88a is closed by means of a plug as shown in Fig. 16.

From groove 89 the oil flows through one or more Z-shaped cross grooves 99 to a second circular groove 9| similar to groove 89 but located near the opposite end of the cylinder block. From these two circular grooves 89 and 9| oil is distributed to each of the sets of plungers l1 and I6 by means of holes 92 drilled in cylinder block 5 opposite each of the cylinder liners 6 and at appropriate locations spaced appropriate distances from each side of the centers of the cylinders (see Figs. 2 and 1). Holes '92 communicate with circular grooves 93 in the cylinder walls through holes 94 in the cylinderliners thereby lubricating the surfaces of the plungers l6 and H.

The plungers are hollow in order to save weight and the slippers 48 and their mounting sockets are lubricated by oil under pressure supplied through the hollow plungers from grooves 93. To accomplish this, each of the plungers l6 and II has a circular groove 95 cut in its surfaces, which for an instant during each reciprocation registers with cooperating grooves 93 and permits a small volume of oil to enter the hollow plunger through a hole 96 at the bottoms of groove 95. The oil from the interior of the plunger flows through a shallow longitudinal groove 91 (see Fig. 1 at the right) in the surface of the body of retainer 53 for holding the slipper 48 in place. The oil passing-through this groove lubricates both the socket surface of the slipper and its bearing surface with the wobble plate. Small radial grooves 48a cut in the slipper bearing face with the wobble plates (Figs. 1 and 16) allow the oil to escape without building up pressure under the slipper which otherwise may lift it away from the wobble plate, causing an undesirable modification of the linear movement of the plunger.

The oil escaping around the plungers and from the slippers is thrown about by the rotation of the wobble plates and forms a mist which lubricates the ball bearings I2 and I4 supporting the drive shaft and the wobble plates. This oil collects at the bottom of the pump housing, the oil at the rear part being allowed to drain to the front section 2 through holes (not shown) drilled longitudinally through the cylinder block 5. The oil accumulating at the bottom of the front housing section 2 finally drains back to the lubricating system of the engine through holes 98 drilled in the web supporting the front ball bearing I2.

When pumping liquid of extremely low viscosity which readily penetrates minute passages and which also adversely affects the lubricating qualities of oil, it is important to prevent contamination of the engine and pump lubricating oil by such liquid. Accordingly the cylinders 8 at their ends in which plungers l'l operate are provided with leak-off grooves 99 which are placed a suitable distance from the lubricating oil grooves 93 as shown in Fig. 2. Grooves 99 are placed in communication with inlet openings 240 by holes I00 and IOI, drilled through the wall of cylinder 6 and the outer portion of cylinder block 5, and by a longitudinal groove I02 cut in the surface of cylinder block 5 and extending to opening 24a.

Any gasoline which leaks past the end of plunger ll towards the lubricating oil grooves 93 is thus trapped by leak-off grooves 99, which being at inlet pressure, provide an escape for the gasoline and prevent any tendency for it to leak beyond grooves 99. In connection with the plunger l6 which controls the inlet ports 22 there is no such tendency for the gasoline to leak to the oil pressure grooves 92 because the only time 9 leakage may occur is when the inner ends of these plungers have closed ports 22 so that if any leakage occurs it merely goes back to these inlet ports.

Referring again to the eiiect of varying the offset angle of the fixed stroke wobble plates l9 and 20, it will be understood that change in this offset angle produces a change in the relative motion of the two opposed plungers it and I1 and that such relative motion determines the extent of shrinkage and expansion of the pumping space l8. This relative motion. that is. the extent to which plungers I. and II approach and 'recede from each other during each revolution of the pump shaft determines the amount of shrinkage and expansion of the pumping space and measures the eiiective output of the pump. The maximum relative motion of plungers l6 and I1 occurs when the wobble plates are offset by an angle of 180 so that the plungers are moving inwardly at exactly the same time, the ends of the two plungers coming together as close as is permissible according to good construction and manufacturing practice.

Such maximum relative motion of the two plungers does not, however, produce the maximum pump output because of the intake ports 22, these ports having to be closed by the advance of plunger l6 before the effective stroke of the pump can commence.

This is illustrated in the diagram shown in Fig. 10 in which the vertical distance from the top horizontal line to the bottom horizontal line represents the maximum separation of the inner ends of plungers l6 and I I. The distance horizontally from the left to right in the diagram is laid out in degrees of angular movement for a complete rotation of the pump shaft. The shaded portion at the top represents the width of inlet ports 22. The upper, continuous line curve, indicated by reference numeral PIG represents the motion of the inner face of plunger l6 and the lower curves represent the motion of the inner faceof plunger I! with the wqlgble plates ofiset at different angles. .Th dottedlower curve-Pi! ()"represents the movement of the inner face of plunger l1 when the offset angle of the wobble plate is 0, or in other words, when the wobble plates are in phase with each other. Comparing this curve with curve PIG it will be seen that they are parallel at all points and consequently that there is no relative motion between them and the pump has no effective stroke.

It will be understood that when the wobble plates are set at some angle other than 0, the effective stroke commences at the point where the inlet ports 22 are closed by the end of plunger l6, and terminates when the two plungers l8 and II have reached their point of closest proximity and commence to recede from one another. Between these two points liquid is being forced through the outlet port 39 and check valve 42 into outlet chamber 31. Hence, referring to the dotand-dash curve Pll (180) of Fig. 10 and comparing this with curve Pl ,at the instant the inlet ports 22 are closed by plunger IS, the inner face of plunger I1 is at the position represented by numeral I03 and th faces of the two plungers at this instant are separated by a distance indicated by the reference character A. The 'pump continues to deliver liquid until the pump shaft has rotated through an angle of 90, at which instant th two plungers have approached one another until they are separated only by the distance B, after which the plungers commence to recede from each other. The effective stroke, therefore, with the wobble plate set 180 out of phase, is indicated by the difl'erence between the lengths A and B. that is, effective stroke=A-B.

If, however, we reduce the offset angle of the wobbl plates from 180 to 120 as shown by curve P" (120) of Fig. 10, the distance A1 which separates the faces of the plungers at the beginning of the effective stroke is considerably more than the distance A which separated them when the wobble plates were offset 180. Although the distance Bl which separates the plungers at the end of the eflective stroke is somewhat greater than the distance B, the effective stroke, A1-B1, is greater than when the wobble plates were set 180 apart. In other words, by decreasing the phase angle of the wobble plates the pump output is increased.

Figs. 11 and 12 show diagrams similar to the central part of Fig. 10 illustrating the length and duration of the effective stroke of the pump at two other oflset angles of the wobble plates. In Fig. 11, A2-B2 indicates the effective stroke of the pump with the wobble plates set at 20, the duration of the output stroke being of pump shaft rotation. In Fig. 12, A-;Ba indicates the effective stroke with the wobble plates set at 65 and the duration of output being 147 It will be noticed that the length in degrees of the delivery period varies inversely with increase in output (from just below at output nearly zero, to 120 of rotation at maximum output). This results in a smooth, substantially non-pulsating flow at all pump outputs, even down to its lowest output and even when operating at slow speed; the increase in the delivery period with decrease in pump output brings about longer overlapping of the delivery periods of the several cylinders when the pump is operating at low outputs than when operating in its upper capacity range.

The variation in the effective stroke of the pump with change in oifset angle of the wobble plates isshown in Fig. 13, the vertical distances of'the diagram indicating the effective stroke and the horizontal distances the phase displacement of the plates. From this curve it will be seen that the output reaches a maximum when the wobble plates are offset at an angle at 120 and after that decreases, the output with the wobble plates at 180 being substantially the same as when the wobble plates are at an angle of about 62 It will also be observed that with an offset angle of from 0 to about 65 the variation of the curve from a straight line is substantially negligible. With a pump having such an inherent characteristic. therefore, the simple linkage mechanism shown in Fig. 1 for adjusting the movement of the offset adjusting member 68 can be successfully used. Hence this mechanism is so constructed as to provide a change in the ofiset angle of the wobble plates 19 and 20 from 0 to a maximum of about 65 with an angular movement of output control lever l5 from 0 to 65.

It may also be desired to obtain a larger output without increasing the size of the pump, by using, for instance, an offset angle of 90 of the wobble plates or even by using the maximum possible trol shaft, then the modified form of control mechanism shown in Fig. 17 can be employed. This mechanism may be arranged to move offset angle adjusting member 68 a sufllcient distance to produce a maximum of 120 offset of the wobble plates although, like the mechanism of Fig. 1, it may also be arranged to produce smaller maximum offset angles. 7

In the modified control mechanism of Fig. 17

the output control lever lie is fixed on the end of shaft 15a, which, like shaft I5, projects through the wall of the rear housing section 3. Inside the housing there is fixed to shaft 15a a cam arm I 04 having a slotted cam I05. Cam I05 engages a roller I06 mounted on a pin I01 which is fixed near the outer end of an arm I08 pivoted at its lower end at I09 to a boss formed on the inside of housing section 3. In its opposite end arm I08 is also connected by means of a link H to member 80 on offset adjusting member 68.

As cam arm I 04 is rocked from the full line position shown in Fig. 17 to the dotted line position by the movement of lever Ia, offset adjusting member 68 is shifted from one end of its range of movement to the other. The full line position corresponds to maximum pump output and the dotted line position to zero output. The shape of cam surfaces I05 are such as to compensate for the deviation of the curve shown in Fig. 13 from astraight line so that for equal increments of angular movement of lever lie: the output of the pump will be increased or decreased by exactly the same amount. I

In connection with the general arrangement of the pump mechanism, it will be understood that sleeves 63 and 68 which support the wobble plate cams 20 and I9 fit closely the exterior surface of pump shaft 2| and are of suflicient length to prevent any longitudinal rocking movement of the sleeves on the shaft due to the unbalanced forces operating near the peripheries of the cams caused by the operating resistance of the pump plungers. In other words, the structure is substantially rigid. Also it will be understood that the main pump ball bearing I2 and I4 are of a type which will resist the end thrust which is caused by the operating resistance of the plungers. These bearings therefore prevent the outward shift of sleeves 63 and 64 and maintain the teeth of sun gears 64 and 81 in engagement with gears 59 of the differential mechanism.

Due to the fact that the wobble plate cams l9 and 20 tend to rotate to the in-phase, or 0 offset position, it will always require the application of a degree of force to the output control lever IS in order to maintain the pump setting at any angle other than the zero output position. The lead angle of the helical splines 60 and I0, however, is very small and consequently the end thrust or pressure which must be maintained on offset adjusting member 60 is not objectionable.

When pumping volatile fluids, such as gasoline, in order to obtain accurate control of the output it is important that the pumping space be filled with solid" liquid (that is, all liquid and no vapor) when the delivery of liquid through the outlet valve commences. The vapor eliminator previously referred to removes the bulk of the vapor,but pressure variations, the velocity of the fluid within the pump itself, and temperature affect the vapor formation in the pump passages and in pumping space I8 of each cylinder. If not removed, such vapor may cause 12 appreciable variation in the volumetric output of the pump.

By admitting the fluid through ports 22' in the cylinder walls and controlled by one of the plungers, such vapor is given an opportunity to leav pumping space I8 before delivery through th outlet valve commences. These ports are of considerable size relative to the size of the pumping space and, as these ports remain open during the first part of the compression stroke of this plunger, some of thefueLand substantially all of the vapor are forced out so that when the plunger closes the ports there remains only "solid" liquid within pumping space I8.

When used as a fuel injection pump the pump of the present invention may develop a pressure of from about 200 to about 400 pounds per square inch, depending upon the-characteristics of the engine with which it is to be used. For other hydraulic applications, however, the pump may be arranged to develop very'much higher pressures if desired. There is substantially no limit to its operating pressure.

The pump of the present invention is inherently balanced and can be operated at high rotative speeds; for example, in the neighborhood of 5,000 R. P. M. Consequently the pump has a high I volumetric output per unit of weight.

When a pump of this sort, that is, a variable output positive displacement pump, is used as a fuel injection pump, one of the most important considerations is the maintenance of accurate metering under varying conditions. In other words, it is not only important that the output shall be accurately under the control of the capacity-varying member but that straight line delivery, or equal increase in delivery with equal increases of speed, shall be maintained. One of the sources of interference with such operation in pumps of this kind is the formation of vapor within the working space of the pump on the intake stroke which changes its volumetric efliciency.

In the pump of the present invention such change is substantially prevented because of the unusually large inlet port area in relation to the volume of the working space or pump displacement. This keeps down the velocity of liquid flow through the inlet ports thereby preventing such a drop of pressure within the working space during intake as would tend to cause vapor formation. In addition, plungers I6 are arranged so as to move at high velocity during both the opening and closing of inlet ports 22, thereby providing especially quick opening and closing of the inlet ports. Consequently the pump has a substantially straight line delivery with change of speed. Because of the good "breathing ability of the cylinders there is substantially no change in volumetric efiiciency with change in speed.

It will be understood that the foregoing disclosure has been made for the purpose of explaining the construction and operation of the pump and that changes can be made without departing from the spirit and scope of the invention which are set forth in the appended claims.

I claim:

1. A pump comprising a pair of plungers, stationary cylinder walls to receive the plungers, the inner ends of said lungers cooperating in a common working space, a rotary fixed stroke wobble plate cam to drive each plunger, said cams having a common axis of rotation, pump operating means to rotate said cams, and means actuatable while said cams are rotating for varying 13 the phase relationship of said rotating cams thereby varying the output of the pump,

2. A pump comprising a pair of plungers. stationary cylinder walls to receive the plungers, the inner ends of said plungers cooperating in a common working space, two fixed stroke cams to drive the respective plungers, a common driving shaft for said cams, means actuatable while said shaft is rotating for turning one of said cams on the shaft and means operatively connected therewith for turning the second cam by a. like amount in the opposite direction to change the phase relation of the plungers and vary the pump output.

I 3. A pump comprising a pair of plungers, cylinder walls to receive the plungers, the inner ends of said plungers cooperating in a common working space, a pump operating shaft, a air of fixed stroke wobble plate cams to drive the respective plungers and means for adjustably mounting the cams on the pump shaft comprising a differential gear spider carried by the shaft, a planet pinion rotatable thereon, a pair of sleeves on the shaft on opposite sides of the spider, each of said sleeves having a sun gear whose teeth mesh with said planet pinion, one of said wobble plates being secured to each of said sleeves, and an adjusting member longitudinally movable with respect to said shaft and having a cam connection therewith to cause rotation of said member with respect to the shaft during such longitudinal movement, and a connection between said member and one of said sleeves to impart such rotational movement thereto, said differential gearing causing the second sleeve and the wobble plate cam thereon to rotate a corresponding amount in the opposite direction.

4. A pump comprising a stationary cylinder, a pair of plungers operating from the opposite ends thereof and defining the pump working space between their inner ends, a fixed stroke rotary wobble plate cam to drive each plunger, said cams having a common driving shaft, and means actuatable while the pump is operating for varying the phase relationship of said cams thereby varying the output of the pump.

5. A pump comprising a cylinder, a pair of plungers operating from the opposite ends thereof and defining the pump working space between their inner ends, two fixed stroke cams to drive the respective plungers, a common driving shaft on which said cams are mounted, means actuatable while the ump is operating for varying the angular position of one of said cams on said shaft and means operatively connected therewith for changing the angular position of the second cam by a like amount in the opposite direction to change the phase relation of the plungers and vary the pump output.

6. A pump comprising a cylinder, a pair of plungers operating from the opposite ends thereof and defining the pump working space between their inner ends, a pump operating shaft, a pair of fixed stroke wobble plate cams to drive the respective plungers and means for adjustably mounting the cams on the pump shaft comprising a differential gear spider carried by the shaft, a planet pinion rotatable thereon, a pair of sleeves on the shaft on opposite sides of the spider, each of said sleeves having a sun gear whose teeth mesh with said planet pinion, one of said wobble plates being secured to each of said sleeves, and an adjusting member longitudinally movable with respect to said shaft and having a cam connection therewith to cause rotation of said member with respect to the shaft during such longitudi- 14 nal movement, and a connection between said member and one of said sleeves to impart such rotational movement thereto, said differential gearing causing the second sleeve and the wobble plate cam thereon to rotate a corresponding amount in the opposite direction. o '7. In apparatus of the class described, a wobble plate cam having a lane bearing face. a shaft therefor, and a member driven by said cam having a, slipper engaging said bearing face, said slipper having a center of oscillation on said driven member which is substantially in the plane of said bearing face.

8. In apparatus of the class described, a wobble plate cam having a plane bearing face, a shaft therefor, a member mounted to reciprocate in a path parallel to said shaft, and a slipper to interconnect said cam anddriven member coacting with the bearing face of the cam, said slipper having with the driven member a universal connection whose center of oscillation is substantially in the plane of said bearing face.

9. In apparatus of the class described, a wobble plate cam having a plane bearing face, a shaft therefor, and a member driven by said cam having a slipper engaging said bearing face, said slipper having a semispherical socket connection with said driven member, the center of said socket being substantially in the plane of said bearing face.

10. In apparatus of the class described, a pair of plungers, cylinder walls to coact therewith, the inner ends of said plungers cooperating in a common working space, a wobble plate cam to drive the outer end of each of said plungers, means for mounting said cams on the shaft for angular adjustment thereon with respect to one another while the pump is operating to change the phase relation of the pistons and thereby vary the pump output, and a slipper to drive each of said plunge ers from its adjacent wobble plate cam coacting with the bearing face thereof, said slipper having a universal connection with the outer end of its plunger, the center of oscillation of said universal connection being substantially in the plane of the respective bear-ing face of the wobble plate cam.

11. In apparatus of the class described, a cylinder, a pair of plungers operating from the opposite ends thereof and defining between their inner ends a pumping space, a shaft parallel with the axis of said cylinder, a wobble plate cam to drive the outer end of each of said plungers, means for mounting said cams on the shaft for angular adjustment thereon with respect to one another while the pump is operating to change the phase relation of the pistons and thereby vary the pump output, and a slipper to drive each of said plungers from its adjacent wobble plate cam c0- acting with the bearing face thereof, said slipper having a universal connection with the outer end of its plunger, the center of oscillation of said universal connection being substantially in the plane of the respective bearing face of the wobble plate cam.

12. In apparatus of the class described, a pair of plungers, cylinder walls to coact therewith, the inner ends of said plungers cooperating in a common working space, an inlet port controlled by one of said plungers, oil grooves in the cylinder walls surrounding each of said plungers, means for supplying oil under pressure to the oil grooves to lubricate the plungers, and a second groove surrounding the plunger which does not control the inlet port, said groove being disposed inwardly from the oil groove for said plunger, and means placin said second groove in communication with the inlet port to return liquid leaking along the surface of the plunger to the inlet and prevent it from mixing with the lubricating oil.

13. In apparatus of the class described, a cylinder, a pair of plungers operating from the opposite ends thereof and defining between their inner ends a pumping space, the cylinder having an inlet port controlled by one of said plungers, oil grooves in the cylinder walls surrounding each of said plungers, means for supplying oil under pressure to the oil grooves to lubricate the plungers, and a second groove surrounding the plunger which does not control the inlet port, said groove being disposed inwardly from the oil groove for said plunger, and means placing said second groove in communication with the inlet port to return liquid leaking along the surface of the plunger to the inlet and prevent it from mixing with the lubricating oil. v

14. In apparatus of the class described, a cylinder, a plunger adapted to reciprocate therein, a pump shaft parallel with the axis of the cylinder, a wobble plate cam rotated thereby for actuating the plunger, a slipper universally pivoted on the outer end of the plunger to interconnect the plunger and the wobble plate cam, and means for lubricating said slipper comprising an interior longitudinal passage in said plunger in communication with said slipper, a passageway through the wall of the cylinder supplying oil under pressure to the surface of the plunger, and an opening from the surface of the plunger to said interior longitudinal passage adapted to register with said oil pressure passageway at each reciprocation of the plunger so as to introduce a small quantity of oil into the interior of the plunger at each reciprocation thereof.

15. In apparatus of the class described, a housing having a central longitudinal bore, a circular inlet passage for liquid to be pumped and a circular outlet passage arranged parallel with one another within said housing, a plurality of inlet ports spaced around the interior of said bore and communicating with said inlet passage, a plurality of outlet ports similarly spaced and connected to said outlet passage, 3, cylinder block positioned within said bore having a central axial opening therethrough, a plurality of cylinders in said block arranged axially thereof in a circular row outside the central axial opening therein, a pump shaft passing through said axial opening, a pair of plungers operating from the opposite ends of each cylinder and defining between their inner ends a pumping space, a pair of wobble plate cams carried by said shaft, one disposed on each side of the cylinder block and cooperating with the plungers projecting therefrom to actuate the same, each of said cylinders having an inlet passage and an outlet passage adapted to register respectively with said inlet and outlet ports.

16. A pump comprising a pair of plungers,

cylinder walls to receive the plungers, the inner of said plungers cooperating in a common working space, mechanism for reciprocating said plungers, an inlet port arranged to be opened and closed by the inner end of one of said plungers, the second plunger constituting a movable cylinder head defining with the first plunger the extent of said workingspace, and an outlet passage communicating with said working space unaffected by the movement of either plunger.

18. A pump comprising a pair of plungers, cylinder walls to receive the plungers, the inner ends of said plungers cooperating in a common working space, an inlet port arranged to be opened and closed by the inner end of one of said plungers, the second plunger constituting a movable cylinder head defining with the first plunger the extent of said working space, and means for operating the plungers in adjustable phase relationship to vary the pump output, the length of the delivery period of the pump in creasing with decrease of said output.

19. A pump comprising a plurality of pairs of axially alined plungers, cylinders to receive each of said pairs of plungers, the inner ends of the plungers of each pair cooperating in a common working space, an inlet port arranged to be opened and closed by the inner end of one of said plungers of each pair, the second plunger of each pair constituting a movable cylinder head defining with the first plunger the extent of said working space, common means for reciprocating all of the plungers which control the inlet ports of said cylinders, common means for reciproeating all the other of said plungers, and means for adjusting said reciprocating means to vary the phase relationship between the plungers of each of said pairs to vary the pump output, the delivery periods of said cylinders overlapping one another and said overlap being greater throughout the lower range of pump output than in the higher range.

20. A pump comprising a pair of plungers, cylinder walls to receive the plungers, the inner ends of said plungers cooperating in a common working space, an inlet port arranged to be opened and closed by the inner end of one of said plungers, the second plunger constituting a movable cylinder head defining with the first plunger the extent of said working space, means for operating the plungers in adjustable phase relationship to vary the pump output, a groove surround-- ing the end of said second plunger when at the inner end of its stroke, and an outlet port communicating with said groove.

21. A pump comprising a pair of plungers, stationary cylinder walls to receive the plungers, the inner ends of said plungers cooperating in a common working space, two rotary cams to drive the respective plungers, a common driving shaft for said cams, means actuatable while said shaft is rotating for turning one of said cams relatively to the other on the shaft and thereby changing the phase relation of the plungers and varying the pump output.

22. A pump comprising a cylinder, a pair of plungers operating from the opposite ends thereof and defining the pump working space between their inner ends, a pump operating shaft, a pair of fixed stroke wobble platecams to drive the respective plungers, and means for adjustably mounting the cams on the pump shaft including a differential gear mechanism carried by the shaft, a pair of sleeves on the shaft each having operatively connected therewith a gear whose teeth coact with said differential mechanism, one

of said wobble plates being operatively connected with each of said sleeves, an adjusting member longitudinally movable with respect to said shaft and having a cam connection therewith to cause rotation of said member with respect to the shaft during such longitudinal movement, and a connection betwen said member and one of said sleeves to impart such rotational movement thereto, said differential gearing causing the second sleeve and the wobble plate cam operatively connected therewith to rotate a corresponding amount in the opposite direction.

23. A pump comprising a stationary cylinder, a pair of plungers operating from the opposite ends thereof and defining the working space between their inner ends, a pump operating shaft, two rotary fixed stroke wobble plate cams carried by said shaft to drive the respective plungers, a difierential gear mechanism operatively associated with said shaft and serving to interconnect said cams, and means actuatable while said shaft is rotating to adjust said mechanism to turn one of said cams relatively to the other to change the phase relation of the plungers and vary the pump output.

DESIRE J. DESCHAMPS.

REFERENCES orrEn The following references are of record in the flle of this patent:

UNITED STATES PATENTS 

